This invention relates to the separation of olefinic hydrocarbons from close-boiling sulfur-containing hydrocarbons by use of a solvent.
Removal of sulfur, in the form of sulfur-containing hydrocarbons, from a hydrocarbon stream such as a cracked gasoline, is normally accomplished by hydrogenation of the sulfur to hydrogen sulfide. Proposed environmental regulations requiring lower sulfur concentrations in gasoline (possibly as low as 30 ppm) have made such sulfur removal even more critical and commercially important than ever before. However, hydrogenation of hydrocarbon streams containing sulfur-containing hydrocarbons and olefins results in the saturation of olefins, with a resulting costly loss in octane rating. Therefore, a process for separating olefins from sulfur-containing hydrocarbons, allowing hydrogenation of the sulfur-containing hydrocarbons without the costly hydrogenation (saturation) of olefins, would be a significant contribution to the art and to the economy.
It is an object of this invention to provide a process for separating at least one olefin from at least one sulfur-containing hydrocarbon.
It is another object of this invention to provide a process for separating at least one olefin from at least one sulfur-containing hydrocarbon using a solvent.
It is still another object of this invention to provide a process for separating at least one olefin from at least one sulfur-containing hydrocarbon using a solvent in an extractive distillation process.
It is yet another object of this invention to provide a process for separating at least one olefin from at least one sulfur-containing hydrocarbon using a solvent, such as N-hydroxyethyl pyrollidone.
It is a further object of this invention to provide a process for separating at least one olefin from a thiophenic compound.
It is another object of this invention to provide a process for desulfurizing a cracked gasoline without saturating olefins contained therein.
In accordance with the present invention, a process is provided including the steps of:
a) contacting a hydrocarbon feedstock comprising at least one olefin and at least one sulfur-containing hydrocarbon with a solvent stream comprising N-hydroxyethyl pyrollidone in a contacting zone; and
b) removing a first overhead stream comprising at least a portion of the at least one olefin from the contacting zone.
Other objects and advantages will become apparent from the detailed description and the appended claims.